The present invention relates to a time counting control system in which time counting is carried out on the basis of a reference clock signal and various necessary operations are performed under the control of a controller (for example, a read only memory) storing microprograms. More particularly, the present invention relates to a time counting control system in which the reference clock signal is frequency-divided into a given clock signal through counting of the processing operation for executing a plurality of steps of the microprogram outputted from the controller.
By convention, a time counting control system such as an electronic timepiece is constructed such that a reference oscillator oscillates a reference signal with frequency of 2.sup.n, for example, 2.sup.15 =32.768 KHz, and the reference signal is frequency-divided by a frequency-dividing circuit including multistage flip-flops using semiconductor devices such as CMOS into a signal with 1 second period. Such a system is disclosed in U.S. Pat. No. 3,664,118. However, the conventional time counting control system using multistage flip-flop circuits for the frequency-dividing needs a number of stages of flip-flop circuits, being followed by complexity of circuit construction. U.S. Pat. No. 3,788,058 discloses another type of the electronic timepiece. In this system, a time counting circuit for counting a one second signal to obtain the time information is used together with a circulating shift register for storing the time information such as second, minute, hour, etc., and an arithmetic device for arithmetically processing the time information from the shift register. A display device used properly visualizes the time information stored in the shift register. In the time counting control system that the time information stored in the shift register is arithmetically operated in an arithmetic device and then the time information operated is stored again in the shift register, with display of the time information in a display device, the arithmetic operation and the display operation are controlled, with the view of simplifying the circuit construction, by using a read only memory, for example, having microprogrammed control instructions stored, and related peripheral circuits such as an address register. This control system is known. The processing by the micro-instructions needs given time periods of instruction executions.
Accordingly, an object of the present invention is to provide a novel time counting control system with simple circuit construction and using a microprogram controller, in which the execution times of micro-instructions are processed as counting times and the reference signal is frequency-divided by the execution times.
Another object of the present invention is to provide a novel time counting control system of which the circuit for frequency-dividing a reference signal is simplified, the time counting control system having at least time counting function and a controller for storing key operation signals of a keyboard, display operation signals of a display device, and various operation signals in the forms of micro-instructions and for controlling various operations by using the micro-instructions.